1. Field of the Invention
This invention relates to on-grade track switches and more particularly to a self-controlled on-grade track switch that senses the approach of an oncoming train and thereafter automatically controls the positioning and locking of the switch to accommodate passage by the train.
2. The Prior Art
The need for efficient and reliable mass transit systems has long been recognized. Relatively recent efforts to provide efficient mass transit have led to the development of monorail transportation systems for use in and around major centers of activity. Monorail transportation systems have proven to be a viable solution to the transportation needs for large numbers of commuters to and from congested centers of activity.
In an attempt to increase efficiency and reduce cost, designers of monorail mass transit systems have focused attention on efficient utilization of the track. Central to the problem of providing a flexible and low cost track layout is the problem of providing means for switching vehicles from one track to another so as to utilize more track in less space.
On-grade track switches of a Y configuration are well known in the prior art. In this type of device one end of the switch is pivoted where it joins a main track and the other end is free to swing from the main track to a branch track. For example, U.S. Pat. Nos. 313,830, 3,013,504 and 3,106,898. Also known in the prior art are on-grade track switches which utilize a centrally pivoted switch. This type of switch is capable of joining the ends of several main track sections as it rotates in a circular fashion from position to position. For example, see U.S. Pat. No. 2,977,893. Also known in the prior art are on-grade track switches of a Y configuration which are capable of being shifted laterally to provide for branching from a main track to a side track. Examples of this type of device are illustrated in U.S. Pat. Nos. 2,977,892 and 3,735,709.
Relatively recent efforts directed toward increasing the efficiency of mass transit systems through automation have led to the development and use of energized monorail tracks. Vehicles traveling on these types of energized tracks are powered by electricity conducted along the tracks. However, use of energized track systems has further complicated the problems relating to on-grade track switching. Efforts have been made in the past to automatically control the energization and de-energization of on-grade track switching devices while changing their position from one track to another. See, for example, U.S. Pat. No. 3,735,709.
Manual control over the response of an on-grade track switch to an oncoming vehicle renders an otherwise automatic mass transit system less flexible and more dependent upon human control, thereby reducing efficiency and increasing the change for error.